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Re: New dinosaur diversity articles
--- GUY LEAHY <email@example.com> wrote:
> I think it's premature to conclude that
> saurolophines (or lambeosaurs, for that matter) were
> absent from NA in the late Maastrichtian, since none
> of the hadrosaur material from late Maastrichtian
> sediments in Utah, Texas or New Mexico has been
> identified to genus as yet.
True, but I recall a large hadrosaur limb
element-ulna? from the Naashoibito was
Edmontosaurus-like, not lambeosaurine. The Scollard
environment was also pretty far inland, probably more
so than the underlying Horseshoe Canyon, unit 4, which
yielded plenty of lambeosaurs and Saurolophus, yet
Edmontosaurus is the only hadrosaur known from the
Scollard. That suggests it had supplanted the
lambeosaurs and saurolophines even in their preferred
A couple of other points I negleced to make earlier:
Jerzykewiecz considered the Okavango (see below) an
analog for the Nemegt, certainly not North America,
which was generally wetter, and retained very wet near
coastal habitat in the late Maastrichtian.
The Tsagayan environment had lambeosaurs and a
saurolophine, which suggests it was similar to the
inland Horseshoe Canyon, and the Nemegt. It is hard to
believe the Tsagayan is younger than these other
units, considering the accessibility of Asia to
American taxa. Saurolophus migrated much farther into
Asia. Why aren't any American taxa represented in the
Tsagayan? I suggest the Tsagayan immediately preceded
the Nemegt, which suggests at least a partial
replacement of Asian with American hadrosaur taxa, and
both are about mid Maastrichtian.
> Tim Donovan <firstname.lastname@example.org> wrote:
> --- "Jaime A. Headden" wrote:
> > Tim Donovan (email@example.com) wrote:
> > > the end, indicating that
> > other factors* were at work causing extinction.>
> > Tim has yet to prove this, or even show it's
> > likely, without using a
> > small set of a lineage (only lambeosaurs? why not
> > use hadrosaurs?
> I mentioned Saurolophus, not just lambeosaurs.
> > Tim cannot prove his gradual
> > reduction in species without
> > using a small group of dinosaurs from ONE
> > as I have yet to see
> > a globally correllated example from him.
> Some taxa e.g. centrosaurines, were only known from
> one continent but appear totally extirpated in all
> late Maastrichtian NA environments. Only
> chasmosaurines are known from lowland and
> environments by the Lancian. This was a large
> geographical area, not a forest. See Dodson's
> in The Complete Dinosaur. The idea of gradual
> extinction is not new.
> > > "mastered" the lambeosaurs
> > by the late Maastrichtian.>
> > Because there are fewer lambeosaurs
> > and more hadrosaurines
> > in the Maastrichtian, and to use Tim's favored
> > for pterosaur
> > extinction,
> I said nothing about pterosaurs.
> > they were "outcompeted" by their
> > longer-jawed, larger, more
> > efficient hadrosaurine relatives. I do not think
> > they were,
> Nor I, that was the point I tried to make, below.
> as I think
> > Marjanovic used the flavor of competition, I
> > attempted to explain
> > how more hadrosaurines are known from
> > NA than
> > lambeosaurines, as a refutation that diversity was
> > shrinking.
> Diversity declined even among hadrosaurines in NA;
> Saurolophus vanished by late Maastrichtian.
> Rather, one
> > group is replaced by another in the selected area
> > investrigation (there
> > were plenty of Maastrichtian lambeosaurs in Asia,
> Not necessarily of late Maastrichtian age, when the
> bulk of diversity decline occurred. Previously it
> mentined onlist that Godefroit's proposed late
> Maastrichtian age for the Tsagayan reflected a
> misinterpretation of Wodehousia, which represented
> early Maastrichtian of Russia.
> > and likely in Europe as
> > well,
> Pararhabdodon was not a lambeosaur.
> > but it appears fewer hadrosaurines given the
> > brevity in the Nemegt
> Saurolophus was an abundant hadrosaurine; the
> lambeosaur Barsboldia was very rare. What do you
> "brevity in the Nemegt"? Paleomag results suggest it
> lasted over a million years.
> > > late Campanian,
> > apparently in near coastal environments which
> > excluded lambeosaurs.
> > Farther inland, Hypacrosaurus was still abundant
> > about 3 million years
> > later. Ankylosaurids and nodosaurs also appear
> > ecologically separated.>
> > This proves very little. Prior occurance of
> > hadrosaurines to
> > lambeosaurine diminishment is simply a factor of
> > lineages of sister-taxa
> > occupying the same strata and altering geography
> > together. Take the
> > changing climate: in the Maastrichtian, we see the
> > climate shift from the
> > "bayou"-like wetlands into a drier, less-bushy
> > Okavango-like floodplain.
Not in NA.
> Then why did Edmontosaurus fare better than those
> adapted to a drier climate?
> > Suddenly, animals used to browsing must make way
> > grazers. Smaller size
> > for travelling dense vegetation at times makes way
> > for huge size for open
> > areas, high-browsing shifts to low-browsing and
> > Late Cretaceous
> > version of grazing: fern-munching. Even a Savuti
> > lion still pauses at a
> > bull elephant, so a *Triceratops* would make a
> > formidible foe to even an
> > animal 1.5 times bigger than it (I am, of course,
> > speaking of
> > *Tyrannosaurus*).
> > So as climate shifts, we will SEE animals change,
> > populations shift, and
> > new animals take precedence over the old. Using
> > old population for the
> > underlying strata to prove diversity issues for
> > whole ignores the rest
> > of the biome.
> > Cheers,
> > =====
> > Jaime A. Headden
> > Little steps are often the hardest to take. We
> > are too used to making leaps in the face of
> > adversity, that a simple skip is so hard to do. We
> > should all learn to walk soft, walk small, see the
> > world around us rather than zoom by it.
> > "Innocent, unbiased observation is a myth." ---
> > Medawar (1969)
> > _______________________________
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